I also don't really understand your main concern either... but I think if you tell us what you are trying to do, we will be better equipped to assist you.
Agreed... not that I'm claiming I'm knowledgeable enough to help, but I'll bet someone here is.
Electrum, supplemented with a printer interface which blocks until the key has been printed out could work. But I understand that there is no ready-to-use solution yet which automates the process of having keys securely synced before being used on the network.
This might be harder than you think, if you really want 100% foolproofness. Printers can run out of ink, hardware RAID can lie to the OS and claim that data has been written if it thinks its backup batteries are sufficient... there are a lot of what-ifs if you don't go into more details.
What I'm trying to say is that even if there is a client that makes the appropriate sync call, things can still go wrong. At some point, it becomes more about risk management than about 100% guarantees...
Also, for what it's worth, I can say that neither Bitcoin Core nor Armory (my two personal favorites...) force a sync after modifying a wallet file.